Method of driving tunnels in rock



1965 s. H. BRANNFORS E 3,224,203

METHOD OF DRIVING TUNNELS IN ROCK Original Filed Feb. 28, 1961 2 Sheets-Sheet 1 Dec. 21, 1965 's. H. BRANNFORS ET AL 3,224,203

METHOD OF DRIVING TUNNELS IN ROCK Original Filed Feb. 28. 1961 2 SheetsSheet 2 United States Patent 3,224,203 METHOD OF DRIVING TUNNELS IN ROCK Sten Harald Brannfors, Lidingo, and Claes Yngve Hjalmar Alberts, Bromma, Sweden, assignors to AB Skanska Cementgjuteriet, Stockholm, Sweden, a corporation of Sweden Original application Feb. 28, 1961, Ser. No. 92,277, now Patent No. 3,153,510, dated Oct. 20, 1964. Divided and this application Sept. 30, 1963, Ser. No. 312,666 Claims priority, application Sweden, Mar. 4, 1960, 2,231/60 3 Claims. (Cl. 61-45) This application is a division of Serial No. 92,277 filed February 28, 1961.

The present invention relates to a method of driving tunnels in rock by blasting salvos, which are repeated after the muck, i.e., the blasted material has been removed. The invention relates to work in such rock or such parts of rock which are so poor that there is a risk of a fall of rock from the natural arched roof produced by the blasting. In such rock the driving of the tunnel cannot be resumed until the recently blasted length of the tunnel has been reinforced. In the previously com mon method the work has been carried out in the following manner: after the salvo has been fired the rock is scaled which involves freeing with great care stones and blocks by means of a pointed tool, the stones and blocks often locking each other in the form of an arch. Large quantities of material can often be released in this way before it is safe to remove the muck loosened by the blasting fromunder the roof, which is usually between 3 and 6 metres long. After the muck has been removed the length is lined, for example by moving forwardly a multi-section steel casting form which is mounted on a hydraulically controlled carriage by means of which the form can be fitted into its position. End plates are then fitted, and the space between the form and the rock is filled with concrete. A very large quantity of concrete is often required to fill the space in the rock. As a rule the concrete casting is so carried out that the final lining of the tunnel is effected at the same time, and the lining may project several decimetres into the natural arched roof of the rock. Only after this has been done can the driving of the tunnel into the rock be continued.

The invention relates to such a method of reinforcement that the driving of the tunnel can be effected more quickly at the same time as work and material is saved. The invention is based on the realisation that the actual fall of material after the arched roof has been formed by the blasting does not occur until one or more hours have elapsed after the blasting. The reason why the fall of material occurs after a certain delay usually depends on the fact that water gradually penetrates to the roof from the part of the rock lying behind the roof, and only after a time affects the roof in such a way that a fall occurs, for example as a result of stone lock in the roof falling out. The method according to the invention is mainly characterized in that the arched roof in the rock which is formed after a salvo and which is spaced from the muck is stabilised by being coated, preferably by spraying, with concrete before the muck is removed.

It is therefore of importance that the coating of the roof with the concrete binder is carried out as soon as possible after the blasting. No real scaling of the rock is necessary; however, a small amount of scaling may be carried out if it is considered necessary but it ought to be done quickly so as not to delay the stabilisation of the roof. The coating of the roof with concrete is preferably started as soon as the apparatus for doing it can be brought into position in an efficient rapid manner; and it is advantageously performed from a platform positioned 3,224,203 Patented Dec. 21, 1965 under the protection of a previously completed protective roof and above the muck.

During the application of the concrete a layer of concrete is first applied over the whole exposed surface of the arched roof to bind the whole surface as rapidly as possible. This layer is consequently relatively thin and is really in the form of a film of for example 2 or 3 to 8 cm. thick. The thickness of the layer is then systematically increased in one or more coating operations until an arched roof is formed such that it prevents a fall of material from the material behind the roof. The muck is then removed under the protection of this roof, the removal being completed in for example three hours. Immediately after the removal of the muck, the driving of the tunnel can be continued by drilling etc. Before or after or at the same time as the drilling the parts of the arched roof and walls exposed by the removal of the muck can be coated with concrete, for example by spraying so as to complete the protective roof.

It is often advantageous to use, for at least the first coating, a quick setting concrete mixture to which an accelerator, known per so, has been added.

The concrete shell produced in this manner--the protective roof for the following Workhas preferably a thickness of for example, between 5 and 16 cm. In tunnels having a relatively small cross-sectional area it can be regarded as the final roof, whilst in tunnels having a large cross-sectional area it merely serves as a protec tive or provisional arched roof for the following tunnel driving. It may be reinforced with permanent reinforcement which is fitted when the tunnel front, as a result of repeated blasting s-alvos, has been advanced one or more stepsthat is at a later convenient opportunity. This reinforcement may either consist of a reinforced coating of pumped or sprayed concrete of uniform thickness or of spaced apart ribs of reinforced pumped or sprayed concrete. On a further later occasion the reinforced load carrying concrete lining may be completed.

A time plan for the production of a protective roof in an eflicient manner usually permits one blasting salvo per day. An example of such a plan is given below. The times are reckoned from the firing of a salvo at zero time. The loose stones which were thrown outwardly by the blasting are assembled together (the workers in gas masks) between 5 and 30 minutes, preferably within 15 minutes. The spraying apparatus is then moved forward to its work position and eifects a first spraying of the exposed arched roof within 8 minutes and 1.5 hours, preferably within 60 minutes; the whole surface is sprayed and a concrete film having a thickness between 2 and 8 cm., for example 3-5 cm., is produced. The coating is then systematically supplemented by one or more spraying operations within 30 minutes and 4 hours from zero time, for example between 45 minutes and 3 hours, during which time the thickness of the sprayed concrete is increased to between 5 and 20 cm., for example between 10 cm. and 16 cm. The muck is then removed, and this may thus begin a few hours after the blasting under the secure protection of the concrete arched roof. The supplementary spraying of the now exposed wall and roof parts and/ or the drilling for the next salvo can now be begun. This can be so arranged that blasting can be carried out early the following day at the commencement of work.

The invention also relates to an apparatus for carrying out the concrete spraying; the apparatus is mainly characterized in that a concrete projection device is mounted on a platform and has a nozzle whose distance fromthe platform is adjustable and which is turnable in relation to the platform.

The invention is described in greater detail below with reference to the accompanying drawing. FIG. 1 of the drawing is a vertical longitudinal section through a tunnel and a concrete spraying apparatus in operation. FIG. 2 shows the concrete applying apparatus in a side elevation.

The reference numeral 1 denotes the temporary face in the tunnel. The reference numeral 2 denotes the muck after a salvo has just been fired, and by means of which a part L has been blasted. The front part of the tunnel has in the above described manner been provided with a protective arched roof 3, which constitutes a protective covering against a fall and which is for example about to cm. thick. Immediately after the salvo has been fired individual stone blocks which were flung a long way are moved towards the muck, for example by means of a suitable machine, so that a wheeled support 4 for a work platform 5 can be moved to the vicinity of the natural roof formed by the blasting at the length L. The platform 5 is located underneath the protective covering 3. A holder 7 for a concrete supply nozzle 8 is swingably mounted in a horizontal plane on a post 6 on the platform. The nozzle extends substantially radially in relation to the holder 7 which is preferably telescopically extendible, so that the nozzle can be swung in the vertical plane. These movements are controlled by a worker on the platform or from the vehicle 4 or the like. The spray nozzle may be of a type known per se. The dry components of the mixture are supplied through a pipe 9 and water is supplied at the nozzle.

The platform is carried by an arm 10 swingably mounted on the support 4 and a parallelogram linkage 11 similarly mounted so that the platform can, by a hydraulic cylinder 12, be moved upwardly and parallel to itself.

The platform, concrete spray nozzle and the parts which support the latter are shown in a larger scale in FIG. 2. The post 6 consists of a lower part fixed to the platform and a part 21 mounted on the part 20 and rotatable about a vertical axis. In the latter there is a hydraulic cylinder for moving a piston rod 22 vertically; on the upper end of the piston rod 22 the long holder 7 is rotatably mounted about a horizontal axis 23 to swing in a vertical plane. A fitting 24 is fixed to the rear end of the holder 7, and a rod 26 is pivotally attached to the latter fitting and the upper part 21 of the post. The holder 7 consists of an outer part 27 and an inner part 28 longitudinally movable in the outer part. The spray nozzle 8 is mounted at the front end of the inner part 28. A hydraulic cylinder 29 having a piston rod 30 is mounted between the parts 27, 28 and is operative to move telescopically the inner part 28 of the holder forwardly and rearwardly in the part 27.

The nozzle is mounted in a bracket 31, which is by means of a pin 32 pivotally connected to a rod 33. The rod 33 is rotatably mounted in a head 34 on the holder part 28 so that the arm 33 and nozzle are swingable about the longitudinal axis of the holders 27, 28. The swinging can be effected by means of hydraulic turning device, known per se, mounted in the head 34. A hydraulic cylinder 37 is swingable about a pin 36 on an arm which projects radially from the arm 33 and the piston rod 38 is pivotally connected to the bracket below the latters swinging axis 32 on the rod 33. The pipes by means of which the pressure medium is supplied to and conducted away from the hydraulically operating devices in the head 34 and to the cylinder 37 are designated by 40 and 41. These pipes are connected by pipes 42 to a pump driven by an electric motor and housed in a casing 43 mounted on the platform 5. Such hydraulically operated devices and pressure pumps are so well known that they do not require any further description. The same applies to the control of the hydraulic devices. The latter can be set in operation by known means by a person standing on the platform by means of hand levers 44.

FIG. 2 shows also the pipe 9 through which the solid dry components of the cement mixture are supplied to the nozzle. They are forced through the pipes by compressed air. 45 denotes a pipe for water which is supplied to the nozzle 8 at the same time as the dry components and which is mixed with the latter immediately before they are sprayed out through the nozzle. This is necessary with quick setting concrete mixtures and is known per se. Such devices are called cement-gun pneumatic placing machines.

The nozzle can, by means of the apparatus described, be moved to and fro along the arched roof in the tunnel and can be directed to the side or upwardly and in addition forwardly or rearwardly so that the jet of cement mixture emerging from the nozzle can be directed towards every point on the arched roof in the tunnel and in between the wedged stones in the roof so that the latter are rapidly bonded to each other to prevent them falling down. The part of the natural roof along the length L spaced from the muck is now coated by the spraying apparatus with a thin film of preferably quick setting concrete, and the whole surface should be covered as rapidly as practicable.

The supplementary coating with concrete is then effected as described above. The latter can be completed within for example three hours so that the apparatus can be removed and the removal of the muck started. Since the protective roof is thin in relation to completed load carrying concrete lining, which in the methods hitherto used have covered the roof L, the lining presents less obstacle to drilling at the edges of the face 1, so that the drill holes may make a smaller angle with the longitudinal axis of the tunnel. The saw tooth longitudinal section which the wall of the tunnel normally has may now be less marked, and consequently material for completion filling is saved in this respect also.

What We claim is:

1. A method of driving a tunnel in rock comprising, in sequence, blasting rock at the tunnel face thereby creating muck in front of the blasted tunnel face, moving a concrete spray apparatus, having a spray head, into a position such that the operator is under the protection of a previously concrete-lined part of the tunnel roof, said spray apparatus having an effective reach, from beneath the lined part of the roof, outwardly beneath the unlined roof part formed by the recent blasting so that the spray head of the apparatus is under an unlined arched roof part formed by the recent blasting, stabilizing said last-named arched roof by spraying thereon a layer of quick setting concrete, spraying more concrete onto the roof so as to form a protective roof, and removing the muck under the protection of the thus newly stabilized roof, covering the parts of the roof and tunnel wall exposed by the removal of the muck with concrete repeating the above sequence at least once, then reinforcing the temporary roof formed after one of the previous blastings, and then repeating the above sequence of operations.

2. A method of driving a tunnel in rock as defined in claim 1, further characterized by applying a layer of concrete within from 8 to minutes from the blasting to form a temporary roof, removing the muck under the protection of the stabilized roof, concreting the parts of the roof and tunnel wall exposed by the removal of the muck, and repeating the above sequence at least once, and then reinforcing the temporary roof formed after one of the previous blastings.

3. A method of driving a tunnel in rock comprising blasting rock at the tunnel face, assembling the stones scattered by the blasting into a muck pile immediately in front of the blasted tunnel face within 5 and 30 minutes of the blasting moving a concrete spray apparatus into a position such that the operator is under the protection of a concrete lined part of the roof and the spray head is under the unlined arched roof formed by the recent blasting, spraying with concrete the arched roof formed by the blasting within 8 minutes and 90 minutes from the blasting to line the roof with concrete between 2 and 8 cms. thick, spraying within 45 minutes and 180 minutes from the blasting a second coating of concrete onto the arched roof so that the total thickness of the lining is between 10 and 16 cms. thick and a temporary roof is formed, removing the muck under the protection of the temporary roof, and then repeating the above sequence of operations.

References Cited by the Examiner UNITED STATES PATENTS 1,380,400 6/1921 McArthur 6142 6 FOREIGN PATENTS 340,032 9/1921 Germany.

5 OTHER REFERENCES Bulletin 2200 of the Cement Gun C0., Gunite, Allentown, Pa., pub. 1942, pages 54 and 55.

10 CHARLES E. OCONNELL, Primary Examiner.

JACOB SHAPIRO, EARL I. WIIMER, Examiners. 

1. A METHOD OF DRIVING A TUNNEL IN ROCK COMPRISING, IN SEQUENCE, BLASTING ROCK AT THE TUNNEL FACE THEREBY CREATING MUCK IN FRONT OF THE BLASTED TUNNEL FACE, MOVING A CONCRETE SPRAY APPARATUS, HAVING SPRAY HEAD, INTO A POSITION SUCH THAT OPERATOR IS UNDER THE PROTECTION OF A PREVIOUSLY CONCRETE-LINED PART OF THE TUNNEL ROOF, SAID SPRAY APPARATUS HAVING AN EFFECTIVE REACH, FROM BENEATH THE LINED PART OF THE ROOF, OUTWARDLY BENEATH THE UNLINED ROOF PART FORMED BY THE RECENT BLASTING SO THAT THE SPRAY HEAD OF THE APPARATUS IS UNDER AN UNLINED ARCHED ROOF PART FORMED BY THE RECENT BLASTING, STABILIZING SAID LAST-NAMED ARCHED ROOF BY SPRAYING THEREON A LAYER OF QUICK SETTING CONCRETE, SPRAYING MORE CONCRETE ONTO THE ROOF SO AS TO FORM A PROTECTIVE ROOF, AND REMOVING THE MUCK UNDER THE PROTECTION OF THE THUS NEWLY STABILIZED ROOF, COVERING THE PARTS OF THE ROOF AND TUNNEL WALL EXPOSED BY THE REMOVAL OF THE MUCK WITH CONCRETE REPEATING THE ABOVE SEQUENCE AT LEAST ONCE, THEN REINFORCING THE TEMPORARY ROOF FORMED AFTER ONE OF THE PREVIOUS BLASTING, AND THEN REPEATING THE ABOVE SEQUENCE OF OPERATIONS. 